R1:ca1349ab45d8

Add an explicit example of constraining "transaction.search" to the webhook documentation

Summary:
Depends on D19509. Ref T13151. See PHI725. `transaction.search` supports "constraints" and the documentation mentions it in passing, but doesn't really show how to do it, and the method is not automatically self-documenting because it isn't a "real" `*.search` method.

Add an example of how to use the `contraints` parameter to retrieve information about only the relevant transactions.

Also remove a…